An apparatus of the generic kind is known from German patent 12 55 292. As described in U.S. Pat. No. 4,492,551, such apparatuses serve to produce pipes provided with transverse grooves, so-called corrugated tubes. Furthermore, corrugated tubes with helically extending transverse grooves can be produced, as described in German patent 12 42 848. Ribs may be provided instead of the transverse grooves, as can be taken from German patent 37 01 822. The molding of the transverse grooves or ribs is made in a vacuum forming process, i.e. by way of vacuum actuated vacuum slits at least substantially arranged at right angles to the mold space axis. As can be taken from German patent 17 04 715, pipes with flexible sections may also be produced on the apparatus according to German patent 12 55 292. The described pipes may further be formed as compound pipes with an additional inner pipe.
However, if pipes with special profile sections are to be produced, of which at least portions have a profile that can be calibrated, i.e. a profile that could also be produced in stationary extrusion tools, then a production of sufficiently good quality is not possible in a vacuum forming method with an apparatus of the generic kind.